The resources with a are licensed by UC San Diego Library for faculty, staff and students, but they are free to search, and you can limit your results to articles that you can access.
Search for scholarly publications across disciplines & sources: articles, theses/dissertations, books, and more. While it is free to search, a lot of the articles you come across will not be. HOWEVER, many of those articles do list multiple versions, so check those to see if there's a free one.
One of the largest publishers for computer science and electrical engineering, with access to the the IEEE & IEE/IET transactions, journals, magazines & conference proceedings, standards, and ebooks.
To limit your results to free articles and chapters, select Open Access in the the search results.
Another large collection of computer science journals and proceedings and conference proceedings, this one from the Association for Computing Machinery.
You cannot filter or limit your results to open access articles, but it is easy to see the open/free titles when browsing the results (anything without the green "Get Access" button.)
One of our largest collections of science/engineering jourrnals and books, with strong coverage of computer science through series like Lectures in Computer Science.
To limit your results to free articles and chapters, check the Open Access box from the search results.
Preprints for physics, astronomy, mathematics, nonlinear sciences, and computer science. Preprints are scholarly articles that have been submitted for publication, but not peer-reviewed. You might want to check the article title in Google to see if there's is an accepted, published copy.
Very large collection of journals and ebooks, with heavy coverage in science and engineering. Includes Elsevier and associated imprints, including Academic Press.
To limit to free articles, check the Open Access box in the results.